Corn syrup is a sweetener (glucose) made from corn starch. It is often added to foods (especially drinks) to sweeten them.

Cooks, especially candy makers, use corn syrup to prevent melted sugar (sucrose) from crystallizing when cooking or cooling which makes a grainy texture in something that should be smooth like taffy, fudge, or marshmallows.

There is some controversy over the industrial use of corn syrup as a sweetener for drinks, since it goes directly to the blood stream and potentially increases the risk of obesity and diabetes.

High Fructose Corn Syrup (HFCS) is made from corn syrup by using enzymes to convert some of the glucose to fructose.